Known in the art is an internal combustion engine provided with a fuel reformer, an air feeder for feeding air to the fuel reformer, and a fuel feeder for feeding fuel to the fuel reformer and designed to respectively feed fuel and air from the fuel feeder and air feeder to the fuel reformer at the time of engine startup so as to cause an exothermic reaction and to feed reformed gas holding the heat generated in this exothermic reaction to a three-way catalyst arranged in an engine exhaust passage and thereby promote warm-up of the three-way catalyst (for example, see Japanese Patent Publication No. 2008-298000A).